~x{sigil}modifiers[key: value]
~x{sigil}modifiers [key: value]
~x{sigil}modifiers[()]
~x{sigil}modifiers [()]
~x{sigil}modifiers[matched_expression]
~x{sigil}modifiers [matched_expression]
~x{sigil}modifiers[matched_expression,]
~x{sigil}modifiers [matched_expression,]
